Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $67.26   3.723%   $69.7641   $69.76   $69.75   $69.80  
  Purchase #2 $197.79   6.190%   $210.0332   $210.03   $210.05   $210.00  
  Purchase #3 $115.45   9.702%   $126.651   $126.65   $126.65   $126.70  
  Purchase #4 $198.53   4.527%   $207.5175   $207.52   $207.50   $207.50  
  Purchase #5 $157.60   6.424%   $167.7242   $167.72   $167.70   $167.70  
  Purchase #6 $63.74   11.191%   $70.8731   $70.87   $70.85   $70.90  
  Purchase #7 $239.86   11.375%   $267.1441   $267.14   $267.15   $267.10  
  7 purchase totals = $1,040.23       $1,119.7072   $1,119.69   $1,119.65   $1,119.70